Spurge purge tests bovine palates

Goats and sheep can eat leafy spurge. Can cattle be trained to do the same?

More than 1.2 million acres are infested with leafy spurge in Manitoba alone, with an annual estimate loss of over $40 million. Photo:
Jane Thornton

Like a parent convincing kids to eat their vegetables because they’re good for them, Jane Thornton is trying the same approach with getting cattle to eat leafy spurge.

“Contrary to popular belief, leafy spurge is a very nutritious plant, comparable to alfalfa in quality,” Thornton says. “If cattle can become accustomed to eating leafy spurge it may have nutritional benefits and also bump up pasture quality late into the season when most grasses have dropped in feed value.”

Thornton is a Manitoba Agriculture pasture and forage specialist working on a spurge management project at the Manitoba Beef and Forage Initiatives (MBFI) research farm on the outskirts of Brandon in western Manitoba, where spurge invasion has been a major problem.

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Control efforts had another setback this year with the announcement that distribution of Amitrol, the only chemical registered for leafy spurge control, will be discontinued this year.

Other methods have been attempted over the years, including insects and grazing by sheep and goats, which apparently don’t mind the taste of leafy spurge.

However, cattle do. Some studies suggest this is due to chemicals in the plant that don’t agree with the cattle’s digestion system. The MBFI project is looking at whether it’s possible to train them to eat it, perhaps by incorporating eating schedules that allow their digestion system to build up tolerance.

“Either way, it is clear that cattle can incorporate leafy spurge as a minor portion of their overall diet,” says Thornton. “Although exactly how much is unknown. And that is exactly what we are trying to get a handle on.”

The system in the study was developed by Kathy Voth, a graduate student of Fred Provenza of Utah State University, who has been researching the system for over 35 years.

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Thornton says the key is more than a matter of taste but a complex system of the gut speaking to the brain in something called biofeedback. “If the eating experience provides the gut with positive nutrient experience then the brain will register this effect and the animal will have learned a positive association with a certain food.”

If successful this practice could have a number of added benefits such as reductions in leafy spurge infestation, increased pasture carrying capacity, increased pasture diversity and increased cattle nutrition.

Major economic problem

Considered the most noxious of all weeds, leafy spurge first arrived on the Canadian Prairies from Eastern Europe on board early settlers’ ships that were unknowingly carrying contaminated seed.

Spurge quickly gained a major foothold on pastures and fields in Western Canada, and spread continues as the weed has no natural enemies.

According to a 2010 Economic Impact report by Brandon University’s Rural Development Institute, 1.2 million acres in Manitoba are infested with leafy spurge. Much of that infestation can be found in and around pastures, woodlands, riparian areas and rights of way. Some of these areas can be difficult to access with large spraying equipment. But even if they were, chemical treatment can be hit and miss and expensive.

Standing around two feet tall with an extensive root system, leafy spurge has yellowish-green flowers and contains a whitish sap-like fluid, which is the cause of the palatability problem. While goats and sheep don’t seem to mind it, cattle do and tend to avoid areas of pasture where leafy spurge plants proliferate. This lost grazing capacity is considerable — the Brandon University study estimates the value of the lands affected, chemicals needed and other indirect impacts of the difficult weed at $40.2 million a year.

MBFI up and running

The challenge is to have cattle develop a positive association with the nutritional benefits of leafy spurge.photo: Jane Thornton

The leafy spurge research project is one of 25 projects underway this summer at the Manitoba Beef and Forage Initiatives (MBFI) research farm located at three sites near Brandon, Man.

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MBFI leaders and partners say they have been encouraged by the quality of the research and the interest of the producers in the farm’s first field season. The projects were showcased at two events this summer: McDonald’s Canada’s Producer Day and Manitoba Agriculture’s Hay Day.

“MBFI is committed to improving the public’s knowledge of the critical role the beef industry plays in sustaining both the Manitoba economy and in managing valuable ecosystems,” says MBFI president Ramona Blyth, a beef producer from MacGregor, Man. “Advancing and understanding the long-term profitability and sustainability connections for Manitoba’s beef and forage producers will be showcased at our research farms.”

“Increasingly, there is great deal of interest in our commitment toward enhancing the profitability of beef and forage production by evaluating foundational research to the ranch level and transferring the knowledge gained to producers.”

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